Backlights are used as extended area illumination sources in displays such as liquid crystal displays (LCDs). Backlights typically incorporate a light source that includes one or more lamps, a lightguide for producing an extended area light source by extending light from the lamps over the output surface of the backlight, and one or more light management layers such as prismatic light redirecting layers, brightness enhancement layers, reflective polarizer layers, diffuser layers, mirror layers and retarder layers. Lightguides are typically solid and include means for extracting light from the lightguide.